Process of making cellulose pulp in sheet form and apparatus for carrying out the same



April 10, 1934. D DAVIES M1,954,284-

PROCESS OF MAKING CELLULOSE PULP IN SHEET FOR AND APPARATUS FOR CARRYINGOUT THE SAME v Filed Sept. 27, 1932 2 Sheets-Sheet l my. a

RUBBER/v0 1.4.:1 PRESs lY/Yl/RLED Rou.

IN VENT OR Zia/1a B. Dar/6s ATTORNEY April 10, 1934. D. B. DAVIES1,954,284 PROCESS OF MAKING CELLULOSE PULP IN SHEET FORM AND APPARATUSFOR CARRYING OUT THE SAME Filed Sept. 27, 1932 2 Sheets-Sheet 2 23SCREEN ROLL- D/PYEHS K/YURLED ROLL IN VENT OR ATTORNEY PatentedApr.10,1934 I 1 954 2 4.

UNITED-STATES PATENT OFFICE PROCESS OF MAKING CELLULOSE PULP IN SHEETFORM AND APPARATUS FOR CARRYING OUT THE SAME David B'. Davies, Shelton,Wash. Application September 2'7, 1932, Serial No. 635,024 2 Claims. (01;92-68) My invention relate to th process of menu- The air about thefibers acts as a shield which facture of cellulose pulp in th form of ht effectively prevents uniform contact with the which, are subsequentlyto be subjected to the abcaustic sode- The Objection tethis air islargely sor tion or reaction of chemicals in the manufacp s a as tpresence p v ts, y x n,

. ture of other products therefrom, to the article of the P p reactionof the ose fibers With the 60 said process and to the apparatus forcarrying out Caustic soda solution and manifests itself in e saidprocess. preferential absorption in the pulp sheets and in In settingforth my invention, I shall employ, the formation of p This Preferenforpurposes of ciearness and definiteness of 1- tial absorption is due tothe fact that the cellulose lustration and description, the prb1emspresentmaterial has a greater attraction for caustic soda 65 ed in themanufacture of viscose, but it is to be than for Water- This results ina lowering of the d r t d th t my invention is, t t be limited causticsoda concentration in the solution. The to any such specificapplication, but is co-extenit s thought, represent e area of sive withall uses involving 1ik problems fibers which have been incompletelyalkalized by steeping is one of the steps i th manufacture the depletedsolution, i. e., the caustic soda solu- 70 of viscose and briefly may bd fi as th proction of low concentration. Also, there is probess ofexposing the cellulose pulp sheets to the ac a Wieking in Of SolubleOrganicimpurities tion of caustic soda solution of a given strength.which have some color- The u i wate In this, one of the greatdifilculties experienced is meining after losing the caustic soda to thecelluthat of providing for unjform'absorption and lose material,carries, it is believed, these organic 5 action of the said'solutionupon the fibers of the impurities t0 the said b W areas, and thus pulpsheets, i. e., for providing for uniform penetribute to the c0101 0f thebrown p -tration of the solution. In the forming of the Imperfectalkalizetien 0f fib in a me s, pulp sheet, the entertwined fibersconstitute a cording to my b vation (same being best exvery porous bodywith air in and about the fibers. plehstion up to the Present, whichhave been Then, as the sheet is carried through the pressure able toWork olit) gives b w p s}? but rolls for the elimination of moisture andthrough perfect alkslizetion 0f fib s scat e ed throu h the calenderingrolls for ironing out and drying the sheets does not manifest itself asbrown the sheet, a hard surface or skin is formed on the spots, butnevertheless slleh imperieetly alkasheet which holds the air or rendersit difiicult lized fibers are highly bject o a le because the for theair to escape, A ord l t hard incomplete reaction with the caustic sodasolusurface or skin, and the confined air positively tion is reflectedin the carbon bisulphide reaction. hinders the penetration of thecaustic soda solu- Step- When t delicacy of t fi a nts ssui tion. Theprimary object of my invention is to om the spinnerets in themanufacture of ra provide for the release of the air and the uniformfrom the viscose and the refinement of e t p penetration of the causticsoda solution. It is my are considered, the requirement of e y and.purpose to achieve these results by providing the Precision in theinitial steps is bv rdipulp sheet with sich necessary characteristics tnarily the reaction product is subjected to at least cause it to soreact during its regular formation five filtletions to remove Partsimperfectly -l and thereby avoid the expense of separate and lized-Those parts which are not filtered out, independent treatment to securethe stated adpartially Very ute sp t vantages. hole. This createsserious difficulties in the spin- It is of the utmost importance in themanuning Operation and results in Y of low q yfacture of products fromviscose that there should In attempting to solve the a o p and pe ebe apositive uniformity of action of t caustic tration difliculties setforth above, relatively thin soda solution on each individual fib Thsheets have been tried. However, this renders must be a completealkalization or reaction with the process expensive and slows down P ucton the caustic soda solution throughout the entire c s d y. ve it Oftendoes not Solve sheet. Failing in this, then, all subsequentaction h D t0the Presence of the hard with other chemicals is variable, incomplete,and surface skin on the sheet of p p- My aim is to 105 unreliable.Proper alkalization is the key step p v as heavy a sheet as p h s stentof the entire process. The carbon bisulphide will with goo p n not,actupon that part of the fibers which has Also, the attempt has been madeto educe the not reacted completely with the caustic soda solubrownspots by the use of relatively pure caustion. tic soda solution, thatis, the solution is main- L as hemicellulosel tained relatively free ofColloidal impurities, such The quantity of such impurities may vary from.4% to 3.0%. Obviously, to so maintain the solution to this degree ofpurity is expensive, and is not altogether positive and reliable onaccount of the preferential absorption explained above.

I have discovered that in providing a roll with a knurled surface topuncture or fracture the hard surface or skin which develops on the pulpsheets during their formation, or semi-puncture of the sheet, that Iobtain the highly important result of rolling out the high spots andproviding a sheet of more uniform thickness. This also results in acloser hugging of the sheet to the drying roll, thereby more completelyreleasing the water vapor and permitting the drying rolls to be operatedat a lower temperature to obtain the same drying action and therebyobtaining a substantial saving of steam consumed. This expedites thedrying of the pulp. The knurled roller tends to eliminate theundulations which ordinarily characterize pulp sheets, so that theexcessive packing of the fibers occurring ordinarily in the area ofthe'crests of the undulation waves is avoided and a sheet of greateruniformity of thickness results. The effect of the knurled roll is toopen up capillaries or openings as fractures to the surface for theelimination of moisture during drying, and for the release of the airwhen the sheet is wetted, and thereby provides for the uniformpenetration of the chemical solution in the steeping process.

The above mentioned general objects of my invntion, together with othersinherent in the same, are attained by the process illustrated in thefollowing drawings, the same being preferred exemplary forms ofembodiment of my invention, throughout which drawings like referencenumerals indicate like parts:

Figure 1 is a fragmentary view in perspective of a knurled roll and itscooperating rubber faced pressure roll embodying my invention Fig. 2 isa schematic view showing the preferred location of said knurled roll inrelation to the pulp pressure and dryer rolls;

Fig. 6 is a view in longitudinal elevation of said screen and knurledroller combination showing I the spacing means;

Fig. 7 is an enlarged view in elevation of the pulp sheet before passingover the knurled roller;

Fig. .8 is a view of one face of the sheet after being subjected to theaction of the knurled roller;

Fig. 9 is a schematic view showing the puncturing device used after thepulp sheet has passed the dryer rolls.

.The roller 10 is provided with a knurled surface 11. Immediately aboveroller 10 is a roller 12 provided with a rubber face 13, which acts as apressure roller upon the sheet passing over the knurled roller 10.

The combination of theknurled roller 10 and rubber roller 12 (see Fig.2) is preferably located after the last of the pressure rollers 14 and15, and before the guide rollers 16 and 17, which are immediately inadvance of the dryer rollers 18, 19,

20, and 21.

After the pulp sheet is formed and as it issues from the pressurerollers 14 and 15, the surface of the pulp sheet 22 is undulatory, asillustrated in Fig. 7.

The nature of the pulp sheet 22 is such that there is formed by theaction of the rollers a hardened surface or skin. The knurled rollersoperate to puncture or fracture this skin and provide the sheet withcapillaries or small openings by means of which the release of themoisture is facilitated. Also, the knurled roller tends to operate inpressing out the crest portion of the undulations and fill in thevalley, portions of the undulations, thereby rendering the sheet moreuniform in thickness. This results in the sheet hugging more closely thedryer rollers so that the drying is expedited, as it provides a muchgreater contacting of the dryer rolls with the sheet. The face of thesheet (see Fig. 8) has areas where the knurled marks, punctures, orfractures 23 are much more pronounced than other areas 24. By thuspuncturing or rupturing the hard surface or skin of the sheet 22 thepenetration and the reaction of the caustic solution is much moreuniform than when the surface of skin is not so provided with openings.

It has been found that upon cutting the sheets that action of a knurledroller tends to cause the sheet to curl. This is highly objectionable,as it interferes with the automatic cutting and stacking of sheets oneupon each other- To overcome this, and to provide for more efficientlypuncturing and fracturing of the surface of the pulp sheet 22, I providethe combination form of the knurled roller 10 and roller 26, whichroller 26 is provided with a screen facing as shown in Fig. 3. Thisscreen is commonly referred to as wire cloth. The size of the openingsmay vary from 10 to 30 mesh. However, I prefer about 20 mesh as it hasbeen giving very satisfactory results. If the higher mesh is used, thenthe openings are too small, and there is not the development of theopenings in the hard surface or skin which result when a more open meshis used, such as about 20 mesh. If, on the other hand, too low .a meshis used, then the openings are too large and the desired puncturingeffect does not result. screen is secured over the open face of aroller, one edge portion 27 being secured by screws or any othersuitable means irra recess 28 on the face, of the roller 26. The screenor cloth is' then wrapped around the roller 26 and the other edgeportion overlaps the part secured in the recess 28,- the latter edgeportion being sewed down with wire 29, so that a smooth longitudinaljoint is provided. (See Fig. 5.) The V shaped sections 30 are cut out ofthe end portions of the wire cloth roller, and the projecting edgeportions bent over the edges of the ends of the roller 26. Clampingcollar 31 is then secured on the end of the roller by means of screws32, and in this manner the screen is securely held to the roller. Thescreen roller 26 is mounted in place of the rubber roller 12 shown inFig. 1.

The screen roll 26 is supported by the pulp sheet 22 passing betweenrolls 10 and 26. In order to protect against the wire cloth roller 26and the knurled roller 10 damaging each other, in the event that thepulp sheet should break, micrometer adjusting spacing bars 33 and 34 ofestablished construction prevent the rollers 10 and 26 from approachingeach other by a space The wire cloth or considerably less than thethickness of the pulp sheet, but nevertheless of sufficient magnitude toprevent contacting, so that the danger of one roller damaging the otheris eliminated.

Upon running the pulp through between the knurled roller 10 and thescreen roller 26, any curling effect is avoided and a most efficientpuncturing or fracturing of the hard surface portion or skin on the pulpis obtained.

The product resulting from the process above set forth provides for anexceedingly high degree of uniformity in penetration of the caustic sodasolution in the steeping step of the process of the manufacture ofviscose. Moreover, it is characterized by the uniformity of thicknesswhich greatly expedites the drying operation. I am able to producesheets forty-eight one thousandths of an inch in thickness which is arelatively very thick sheet to be used in the steeping process of themanufacture of viscose. This contrasts decidedly with the attempt toovercome the steeping difficulties by providing a very thin sheet. Suchhas been attempted of a thinness of twenty-eight one thousandths of aninch.

In the operation of the knurled roller in connection with either therubber pressure roller 12 or the screen roller 26 avoids unduecondensing or packing of the fibers occurring ordinarily in the midst ofthe undulation waves. The knurled roller 10 operates to provide a sheetof pulp much more uniform in thickness. In thus providing for uniformityof penetration of the caustic soda solution, the preferential absorptionof the caustic soda solution is avoided, together with all of theensuing difliculties in the subsequent chemical steps due to imperfectalkalization of the sheet. Thus, the product embodying my invention ischaracterized by having a more uniform density of cellulose fibers andalso by uniformity of thickness, and also by having the hard surfaceorskin provided with punctures or fractures, whereby capillaries oropenings are provided for more uniform penetration of the caustic sodasolution and the release of the air in and about the fibers.

In Fig. 9, I have illustrated the use of a knurled roll and screen rollupon the pulp sheet after the same has passed the dryer rolls. Theknurled roll 35 in this operation may be similar to the knurled roll 10,however it is preferably provided with sharper knurling. The upper rollhere illustrated may be in the form of the roller illustrated by rollers12 or 26.

This apparatus will permit the puncturing effect to be obtained upon adry sheet as distinguished from the operation upon a wet sheetheretofore discussed. The operation upon a wet sheet permits theadvantages heretofore discussed, such as the hugging of the dryer rollsby the pulp sheet, more effective and efiicient drying by the dryerrolls and the production of a more uniform product as respects thicknessand such wet process is therefore the preferable method.

Obviously, changes may be made in the form, dimensions and arrangementof the parts of my invention, without departing from the principlethereof, the above setting forth only a preferred form of embodiment.

.I claim:

1.'In apparatus for providing a plurality of punctures or semi-puncturesto a cellulose pulp sheet, a knurled roll and a screen faced rollpositioned thereabove in spaced relation, said screen faced roll beingmounted to normally rest upon a pulp sheet passing between said rolls.

2. In the process of making cellulose pulp in the form of sheets whichare to absorb or react with chemicals in the manufacture of otherproducts therefrom, the step of passing said pulp sheet while wetbetween a knurled roller and a roller cooperating with said knurledroller whereby raised portions of said sheet are pressed into depressedportions of said sheet so that said sheet is made relatively uniform inthickness.

DAVID B. DAVIES.

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